Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/miru-zero/zero-brain/xss-cross-site-scriptingnpx skills add miru-zero/zero-brain --skill xss-cross-site-scriptinggit clone --depth 1 https://github.com/miru-zero/zero-brainWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/miru-zero/zero-brain/xss-cross-site-scripting)<a href="https://agentmods.dev/skills/miru-zero/zero-brain/xss-cross-site-scripting"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/xss-cross-site-scripting.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.03760 |
| Opus 5 | $0.00018 | $0.01880 |
| Sonnet 5 | $0.00007 | $0.00752 |
| Haiku 4.5 | $0.00004 | $0.00376 |
Grade A, and why
xss-cross-site-scripting scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
95% identical to xss-cross-site-scripting — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 380 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Cross-Site Scripting (XSS) — Expert Attack Playbook
AI LOAD INSTRUCTION: This skill covers non-obvious XSS techniques, context-specific payload selection, WAF bypass, CSP bypass, and post-exploitation. Assume the reader already knows
<script>alert(1)</script>— this file only covers what base models typically miss. For real-world CVE cases, HttpOnly bypass strategies, XS-Leaks side channels, and session fixation attacks, load the companion SCENARIOS.md.
0. RELATED ROUTING
Extended Scenarios
Also load SCENARIOS.md when you need:
- Django debug page XSS (CVE-2017-12794) — duplicate key error → unescaped exception → XSS
- UTF-7 XSS for legacy IE environments (
+ADw-script+AD4-) - HttpOnly bypass methodology — proxy-the-browser, session riding, CSRF-via-XSS
- XS-Leaks side channel attacks — timing oracle, cache probing,
performance.now()measurement - Session fixation via XSS — pre-set session ID before victim login
- DOM clobbering techniques for CSP-restricted environments
Advanced Tricks
Also load ADVANCED_XSS_TRICKS.md when you need:
- mXSS / DOMPurify bypass — namespace confusion,
<noscript>parsing differential, form/table restructuring - DOM Clobbering — property override via
id/name, HTMLCollection, deep property chains - Modern framework XSS — React
dangerouslySetInnerHTML, Vuev-html, AngularbypassSecurityTrust*, Next.js SSR - Trusted Types bypass — default policy abuse, non-TT sinks, policy passthrough
- Service Worker XSS persistence — malicious SW registration, fetch interception, post-patch survival
- PDF/SVG/MathML XSS vectors, polyglot payloads, browser-specific tricks
- XS-Leaks & side channels — timing oracle, frame counting, cache probing, error event oracle
Before broad payload spraying, you can first load:
- upload insecure files when you need the full upload path: validation, storage, preview, and sharing behavior
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 380 lines · 36 tokens per session scan A eca6d4a2bb85
xss-cross-site-scripting is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 18d ago), licensed MIT. It adds 36 tokens to every session and 3,760 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to xss-cross-site-scripting, differing in 4 lines, and is treated as a copy.
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